1. Field of Invention
The invention relates to a coolant passage connecting apparatus in a machine tool that connects coolant passages for supplying coolant fluid to a tool. More particularly, the invention relates to the coolant passage connecting apparatus that fluid-tightly connects a shaft""s coolant passage formed on a main shaft, and a tool""s coolant passage formed on a tool at an end of the main shaft.
2. Description of Related Art
A known machine tool is structured to eject pressurized coolant fluid from a tip of a tool, which is attached to a main shaft, for cooling and lubricating a workpiece, as well as for removing cutting chips. To eject coolant fluid to a workpiece from an end of a coolant passage formed on a tool, a fluid-tight connection needs to be established between a shaft""s coolant passage formed on the main shaft and the tool""s coolant passage formed on the tool at an end of the main shaft, wherein the tool""s coolant passage includes a coolant passage formed on a tool holder that fixedly holds the tool and is removably mounted on the main shaft.
For the fluid-tight connection between the shaft""s coolant passage and the tool""s coolant passage, a known machine tool has an O-ring or packing/stuffing on the main shaft. For example, when the tool holder is mounted on the main shaft, the O-ring or packing/stuffing presses around the periphery of an opening of the coolant passage in the tool holder. Thus, the coolant passages in the main shaft and the tool holder are fluid-tightly connected using the O-ring or packing/stuffing provided at the main shaft.
However, a sealing member, such as the O-ring and packing/stuffing, which is used for a long period, may sometimes allow coolant fluid to leak out, due to the wear and tear thereof. In this case, the sealing member needs to be replaced. However, in the above-described tool machine it is very difficult to replace the sealing member. For example, Japanese Laid-Open Patent Publication No. 8-155783 discloses the replacement of the O-ring fitted on the inner surface of a coolant supply member at an end thereof, including a coolant passage formed on the main shaft, by removing a detachable member screwed on an end of the coolant supply member. However, the end of the coolant supply member, where the O-ring is fitted, is disposed fairly inward from an end of a housing for the main shaft. Therefore, the replacement of the O-ring at the remote position is difficult and troublesome.
One aspect of the invention is to provide a coolant passage connecting apparatus in a machine tool, the machine tool having a main shaft formed with a shaft""s coolant passage for supplying coolant fluid for a tool attached to a distal end of the main shaft, the shaft""s coolant passage fluid-tightly connecting to a coolant passage formed on the tool, wherein a sealing member prevents coolant fluid leakage by pressing a periphery of an opening to the tool""s coolant passage, that is easily replaced.
According to one aspect of the invention, a coolant passage connecting apparatus is provided in a machine tool. The machine tool has a main shaft formed with a shaft""s coolant passage for supplying coolant fluid for a tool attached to a distal end of the main shaft. The shaft""s coolant passage fluid-tightly connects to a tool""s coolant passage formed on the tool. The coolant passage connecting apparatus may include a sealing member that prevents coolant fluid from leaking outwardly from a connecting portion between the shaft""s coolant passage and the tool""s coolant passage, and a coolant nozzle detachably attached to the distal end of the main shaft. The coolant nozzle is formed with a hollow to be connected to the shaft""s coolant passage and to the tool""s coolant passage while the tool is mounted on the main shaft. The coolant nozzle detachably attaches the sealing member to the periphery of an opening to the shaft""s coolant passage. The sealing member is pressed against a periphery of an opening of the coolant passage of the tool by the coolant nozzle.
In the coolant passage connecting apparatus of the invention, the sealing member is pressed against the periphery of the opening to the tool""s coolant passage when the tool is attached to the main shaft, preventing coolant fluid from leaking outwardly from the connecting portion between the shaft""s coolant passage and the tool""s coolant passage. The sealing member is attached to the coolant nozzle. The coolant nozzle is detachable from the distal end of the main shaft. This structure enables the sealing member and the coolant nozzle to be easily removed together.
The hollow is formed in the coolant nozzle. The hollow is connected to the shaft""s coolant passage and to the tool""s coolant passage while the tool is mounted on the main shaft. In the coolant passage connecting apparatus, the shaft""s coolant passage and the tool""s coolant passage may be fluid-tightly connected with the aid of the sealing member. In addition, the sealing member is removed from the main shaft together with the coolant nozzle, as described above. This enables a user to replace the sealing member with a new one close at hand. If the coolant passage connecting apparatus is applied to a machine tool, coolant fluid leakage may be prevented in the main shaft, and the ease of maintenance improves.
A proximal end of the coolant nozzle is fluid-tightly and slidably inserted into the shaft""s coolant passage. The coolant passage connecting apparatus may further include an urging member that urges the coolant nozzle toward a distal end of the main shaft, and a stopper member that is removably fixed to the main shaft and that stops the coolant nozzle on a side of the distal end of the main shaft by engagement therewith, so that the coolant nozzle is prevented from coming out toward the distal end of the main shaft.
In the coolant passage connecting apparatus, the proximal end of the coolant nozzle is fluid-tightly and slidably inserted into the shaft""s coolant passage. The coolant nozzle inserted into the shaft""s coolant passage is urged by the urging member toward the distal end of the main shaft, so that the sealing member is favorably pressed against the periphery of the opening to the tool""s coolant passage, by an urging force of the urging member, especially when the sealing member is provided at the distal end of the coolant nozzle. Thus, coolant fluid leakage may be effectively prevented.
The stopper member is removably fixed to the main shaft against the urging force, stopping the coolant nozzle on a side of the distal end of the main shaft. When the stopper member is engaged with the main shaft, the coolant nozzle is prevented from coming out by the urging force toward the distal end of the main shaft. As the stopper member is removed from the main shaft, the coolant nozzle may easily be removed therefrom. In this structure, coolant fluid leakage may be effectively prevented and the sealing member, which is attached to the coolant nozzle, may be easily replaced.
When the stopper member is removed from the main shaft, the coolant nozzle and the urging member can be removed together from the main shaft on a side of the distal end thereof.
Because the coolant nozzle and the urging member can be removed together from the main shaft on the side of the distal end thereof, upon the removal of the stopper member from the main shaft, the urging member, such as a spring, may be replaced easily, in the cases where the urging member needs to be replaced due to the deterioration thereof with time. This structure enables the urging member to be easily replaced, leading to the improvement in the ease of maintenance for a machine tool.
The urging member is disposed outside of the coolant nozzle. When the urging member, such as a spring, is disposed inside of the coolant passage, the urging member may be subjected to corrosion by the coolant fluid. In the coolant passage connecting apparatus of the invention, the urging member is disposed outside of the coolant nozzle, so that the urging member will not be subjected to corrosion by the coolant fluid. For example, when a spring is used as the urging member, the spring conventionally needs to be made of a material having an excellent corrosion resistance, such as stainless steel (SUS), to prevent the corrosion of the spring by coolant fluid. However, a spring made of widely-used low-cost materials, such as steel, can be used in the coolant passage connecting apparatus of the invention, because the spring will not be subjected to corrosion by the coolant fluid. Thus, the manufacturing cost is reduced while the corrosion of the urging member is prevented.
The proximal end of the coolant nozzle is fluid-tightly and slidably inserted into the shaft""s coolant passage. The coolant passage connecting apparatus may further include a second sealing member provided in a vicinity of the proximal end of the coolant nozzle. The second sealing member retains a fluid-tightness between an inner wall of the shaft""s coolant passage and an outer periphery of the coolant nozzle.
When the proximal end of the coolant nozzle is fluid-tightly and slidably inserted into the shaft""s coolant passage, it is preferable that a sealing member is provided to retain the fluid-tightness between the inner wall of the shaft""s coolant passage and the outer periphery of the coolant nozzle. Such a sealing member may prevent coolant fluid from leaking out at the proximal end of the coolant nozzle, so that the second sealing member is provided in the coolant passage connecting apparatus. The second sealing member may be removed from the main shaft together with the coolant nozzle when the coolant nozzle is removed from the main shaft.
By removing the second sealing member from the main shaft together with the coolant nozzle, the second sealing member may be replaced with new one close at hand, similarly as the sealing member is replaced. In the coolant passage connecting apparatus of the invention, coolant fluid leakage may be effectively prevented and the ease of maintenance in a machine tool improves.